def scalar(value):
"""Expression representing a scalar value.
Parameters
----------
value : bool, int, float or string
Python value of the scalar. Note that only a subset of types are
currently supported.
Returns
-------
scalar_expr : Expression
"""
return Expression._scalar(value)
def field(name):
"""Reference a named column of the dataset.
Stores only the field's name. Type and other information is known only when
the expression is bound to a dataset having an explicit scheme.
Parameters
----------
name : string
The name of the field the expression references to.
Returns
-------
field_expr : Expression
"""
return Expression._field(name)